Generally, an electronic circuit apparatus is provided to control operation of various electrical devices mounted at a vehicle or the like.
FIG. 7 shows an engine ECU 100 as a conventional electronic circuit apparatus. The engine ECU 100 has a circuit board 101 where circuit components (not shown) are mounted. The circuit board 101 is fixedly accommodated in a casing 102. The casing 102 includes an accommodation portion 103 and a cover 104. The cover 104 is attached to the accommodation portion 103, after the circuit board 101 is held in the accommodation portion 103. Thus, the circuit board 101 is fixed in the accommodation portion 103.
A connector 105 for electrically connecting the engine ECU 100 with an external electrical circuit is attached to the circuit board 101. The connector 105 is partially exposed to the outside of the casing 102 from an opening 104a arranged at the cover 104 to be capable of electrically connecting with the external electrical circuit, while the circuit board 101 is fixed in the casing 102.
However, in this case, it is difficult to prevent foreign matter such as water from entering the casing 102. Moreover, there is minute gap between the casing 102 and the circuit board 101. Thus, when the engine ECU 100 is excited by an external vibration, the circuit board 101 will vibrate in the casing 102 to cause unusual sound (noise), or the circuit components will deviate from the circuit board 101, or the like.
Furthermore, because the construction member number of the conventional electronic circuit apparatus is large, the mounting labor will increase.